1. Field of the Invention
This invention relates generally to optical amplifiers, and more particularly to high-efficiency broadband Raman amplifiers with high signal output power.
2. Description of the Related Art
The maximum number of dense wavelength-division-multiplexed (DWDM) signals that can be transmitted over a single optical fiber has been rapidly increasing over the last few years. This trend coupled with an increasing data rate per signal has led to a profound increase in the amount of signal power propagating through such optical fibers. This has created a simultaneous demand for large bandwidth and high output power from the optical amplifiers used in such systems. To produce practical optical amplifiers with high output powers, the efficiency of such amplifiers must be maximized. This reduces the amount of optical pump power required as well as the amount of electrical power and cooling needed.
Erbium-doped fiber amplifiers (EDFAs) are a relatively mature technology and several high-efficiency designs have been disclosed (1999 OFC Technical Digest papers WA6 p16-18 and WA7 p19-21). The amount of bandwidth such amplifiers can produce, however, is fundamentally limited by the physics of the erbium atoms that produce the optical gain in such devices. Raman amplifiers offer an alternative to EDFAs. While many Raman amplifiers have been disclosed, the efficiency of such devices is rarely mentioned. One paper that does discuss efficiency (1999 OFC Technical Digest paper WG5 p114-116) uses a single extremely high-powered pump laser to achieve high optical pump-to-signal conversion efficiency. While the pump-to-signal conversion efficiency of this amplifier was large, the pump laser itself was fairly inefficient requiring much more electrical power and cooling than a laser-diode-pumped design would. The amplifier gain bandwidth was also too limited to be practical for DWDM applications.
There is a need for improved high efficiency Raman amplifiers. There is a further need for efficient broadband Raman amplifiers with sufficient powers that support many dense WDM channels.
Accordingly, an object of the present invention is to provide an improved Raman amplifier apparatus.
Another object of the present invention is to provide an efficient Raman amplifier apparatus.
Yet another object of the present invention is to provide an efficient, broadband Raman amplifier apparatus.
A further object of the present invention is to provide an efficient, broadband, high power Raman amplifier apparatus.
Another object of the present invention is to provide an efficient broadband Raman amplifier apparatus that is suitable for WDM applications.
These and other objects of the present invention are achieved in an amplifier apparatus that includes an optical transmission line with a Raman amplification region that provides a pump to signal power conversion efficiency of at least 20%. The Raman amplification region is configured to amplify a signal with multiple wavelengths over at least a 30 nm range of wavelengths. A pump source is coupled to the optical transmission line. An input optical signal is amplified in the Raman amplification region and an output signal is generated that has at least 100 mW more power than the input optical signal.
In another embodiment, the present invention is an amplifier apparatus including an optical transmission line with a Raman amplification region that provides a pump to signal power conversion efficiency of at least 20%. A laser diode pump source is coupled to the optical transmission line. An input optical signal is amplified in the Raman amplification region and an output signal has at least 100 mW more power than the input optical signal.
In another embodiment of the present invention, an amplifier system includes at least 32 signal sources that collectively produce an input optical signal. An optical transmission line is coupled to the signal sources. The optical transmission line has a Raman amplification region that provides a pump to signal power conversion efficiency of at least 20%. A pump source is coupled to the optical transmission line. The input optical signal is amplified in the Raman amplification region and the output signal has at least 100 mW more power than the input optical signal.
In another embodiment of the present invention, an amplifier system provides at least 32 signal sources that produce an input optical signal over a wavelength range of at least 30 nm. An optical transmission line is coupled to the signal sources and includes a Raman amplification region. A pump source is coupled to the optical transmission line. The input optical signal is amplified in the Raman amplification region and the output optical signal has at least 100 mW more power than the input optical signal.
In another embodiment of the present invention, an optical signal is amplified in an amplifier apparatus that includes an optical transmission line and a Raman amplification region that provides a pump to signal power conversion efficiency of at least 20%. The optical signal has multiple wavelengths over at least a 30 nm range of wavelengths. The optical signal is introduced into an input of the optical transmission line. The input optical signal is amplified and the output signal has at least 100 mW more power than the input optical signal.
In another embodiment of the present invention, a method of amplifying an optical signal provides an amplifier apparatus that includes an optical transmission line, an input and a Raman amplification region that provides a pump to signal power conversion efficiency of at least 20%. The optical signal is introduced into the input. The Raman amplification region is pumped by at least one diode laser pump source. The input optical signal is amplified and the output signal has at least 100 mW more power than the input optical signal.
In another embodiment of the present invention, a method of amplifying an optical signal provides an amplifier apparatus that includes an optical transmission line with an input and a Raman amplification region. The amplifier apparatus is pumped with at least a first pump beam. At least 32 signals are introduced into the input as an input optical signal. The input optical signal is amplified and an output optical signal is produced with at least 100 mW more power than the input optical signal.